JPH11141461A - Method of manufacturing rotor for internal gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a rotor for an internal gear pump made of an iron-based sintered material which is slidably housed in a housing made of a high silicon aluminum-containing material, and has durability and sliding parts. Improve the wear resistance. SOLUTION: Work pieces to be rotors 11 and 13 are manufactured through a powder molding step, a sintering step, a straightening step, and a cutting step sequentially. Next, after the workpiece is subjected to a grinding process for improving accuracy, the workpiece is subjected to a steam treatment to form an oxide film 17 on the surface of the workpiece. By thus finishing the coating process, the effect of the oxide coating 17 can be reliably obtained, and the durability performance and the wear resistance of the sliding portion can be reliably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a rotor for an internal gear pump by powder metallurgy.

[0002]

FIGS. 2 and 3 show an example of an internal gear pump used as an oil pump. Reference numeral 1 denotes a housing. The housing 1 includes a housing main body 2 and a cover 4 fixed to the housing main body 2 with bolts 3. A rotor housing space is provided between the housing main body 2 and the cover 4. 5 are formed. A bearing hole 6 is formed in the housing 1 so as to penetrate the rotor housing space 5, and a pair of ports 7, with the bearing hole 6 interposed and facing the rotor housing space 5. 8 are formed. In the rotor housing space 5, an annular outer rotor 11 is rotatably housed in a substantially fitted state. A plurality of teeth 12 are formed on the inner periphery of the outer rotor 11. Further, an inner rotor 13 is rotatably supported inside the outer rotor 11. The inner rotor 13 has a plurality of teeth 14 smaller than the number of teeth of the outer rotor 11 formed on the outer periphery, and a shaft hole 15 formed at the center. A drive shaft 16 fitted into the shaft hole 15 while being prevented from rotating is rotatably supported in the bearing hole 6 of the housing 1. In addition, both rotors 11, 13
Indicates that the rotation axes are offset from each other and that both rotors
The teeth 12, 14 of 11, 13 are in mesh with each other.

When the oil pump operates, the inner rotor 13 rotates together with the drive shaft 16, and the outer rotor 11 in which the teeth 12 mesh with the teeth 14 of the inner rotor 13 also rotates. These rotors 11, 13
, The oil is compressed between the rotors 11 and 13 and the oil is sent from one port 7 (or 8) to the other port 8 (or 7).

The rotors 11 and 13 are generally made of iron. Conventionally, the housing body 2 is generally a cast product made of an iron-based material, but in recent years, an aluminum die-cast product has been used for cost reduction. In the case of the housing body 2 made of an aluminum material, the rotors 11 and 13 made of an iron material are used.
In order to make the thermal expansion coefficient close to that of the above, the material of the housing body 2 contains silicon at a high ratio. The ratio of silicon is
It is 12% by weight or more, for example, about 20% by weight.

As a method of manufacturing the rotors 11 and 13, there is a method utilizing powder metallurgy. In the case of the rotors 11 and 13 incorporated in the housing body 2 made of a material containing high silicon, special consideration is required. Here, the rotor 11, which is incorporated in the housing body 2 made of a material containing high silicon,
An example of thirteen conventional manufacturing methods will be described. First, the raw material powder is compressed by a powder forming press to form a green compact. Next, the green compact is heated by a sintering furnace and sintered. Next, in order to obtain a predetermined size or shape, the work made of the sintered body is pressed by a straightening press to perform sizing, and the work is subjected to cutting. Next, as shown in FIG. 4A, while the housing body 2 is made of a material containing high silicon, the rotors 11 and 13 are used.
In order to improve the durability performance and wear resistance of sliding parts,
The work is subjected to steam treatment to form an oxide film 17 of ferric oxide on the surface of the work, thereby increasing the hardness of the work surface. Heat treatment may be considered as a treatment for increasing the hardness, but steam treatment is used because the accuracy of the heat treatment deteriorates. Further, the work, that is, the sliding portion of the rotors 11 and 13 with the housing 1 is subjected to a grinding process for improving accuracy. This sliding part is the outer rotor 11
Are the both end surfaces and the outer peripheral surface, and the inner rotor 13 is both end surfaces. In FIG. 4A, a dashed line A indicates a portion to be removed by grinding. Reference numeral 18 denotes pores in the work.

However, in this conventional manufacturing method, since the grinding process is performed after the steam process, as shown in FIG. 4B, the oxide film 17 formed by the steam process is shaved by the subsequent grinding process. However, there is a problem that the effect of the oxide film 17 is impaired.

An object of the present invention is to provide a method of manufacturing a rotor for an internal gear pump which can reliably obtain the effect of a film formed on the surface of a work. With the goal.

[0008]

According to the first aspect of the present invention, there is provided an internal gear pump made of a sintered material slidably housed in a housing made of a high silicon content material. In a method for manufacturing a rotor, a powder molding step of compressing a raw material powder to form a green compact, a sintering step of heating and sintering the green compact, and a sintered body obtained by the sintering step And a film processing step of subjecting the work to steam treatment after the grinding step to form an oxide film on the surface of the work.

According to a second aspect of the present invention, there is provided a rotor for an internal gear pump made of an iron-based sintered material which is slidably housed in a housing made of a high silicon aluminum-containing material. In the method, a powder compacting step of compacting a raw material powder to form a green compact, a sintering step of heating and sintering the green compact, and a work made of a sintered body obtained by the sintering step A pressurizing step, a cutting step in which the work is cut after the straightening step, a grinding step in which the work is ground after the cutting step, and a steam treatment in which the work is subjected to steam treatment after the grinding step. And a film processing step of forming an oxide film on the surface of the work.

[0010] By performing steam treatment after the grinding process, unlike the case of performing the grinding process after the steam process, the formed oxide film is not shaved, and the entire manufactured rotor is reliably formed. The state is covered with the oxide film.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a rotor for an internal gear pump according to the present invention will be described below. The manufacturing method of this embodiment can be applied to both the outer rotor 11 and the inner rotor 13. The internal gear pump into which the rotors 11 and 13 manufactured by the manufacturing method of the present embodiment are incorporated is as shown in FIGS. 2 and 3 described above. The housing body 2 is made of an aluminum-based material. However, in order to make the thermal expansion coefficient close to the rotors 11 and 13 made of an iron-based sintered material slidably housed in the housing body 2, a high proportion of silicon is used. It is contained in. The ratio of silicon is 12% by weight or more, for example, about 20% by weight.

In manufacturing the rotors 11, 13, first, the raw material powder is compressed by a powder forming press to form a green compact (powder forming step). Next, this green compact is heated and sintered in a sintering furnace (sintering step). Next, in order to obtain a predetermined size or shape, the work made of the sintered body obtained in the sintering step is pressed by a straightening press to perform sizing (sizing step). Next, the work is subjected to cutting (cutting process). Next, as shown in FIG. 1A, a grinding process for improving accuracy is performed on a work, that is, a sliding portion of the rotors 11 and 13 with the housing 1 (grinding step). The sliding portions are both end surfaces and the outer peripheral surface in the outer rotor 11, and are both end surfaces in the inner rotor 13. In FIG. 1A, a dashed line B indicates a portion cut off by grinding. Reference numeral 18 denotes pores in the work. Next, FIG.
As shown in (b), while the housing body 2 is made of a material containing high silicon, the workpiece is subjected to steam treatment (steam treatment) in order to improve the durability performance of the rotors 11 and 13 and the abrasion resistance of sliding parts. ) To form an oxide film 17 of triiron tetroxide on the surface of the work to increase the hardness of the work surface (coating process). If a heat treatment such as quenching is used to increase the hardness of the rotors 11 and 13, the accuracy may be impaired. However, if steam treatment is used, the accuracy obtained in the preceding grinding step is not impaired.

By performing the steam treatment after the grinding process in this way, unlike the conventional case of performing the grinding process after the steam process, the formed oxide film 17 is not scraped. Therefore, the manufactured rotor 11,
Since the entire surface 13 is reliably covered with the oxide film 17, the effect of the oxide film 17 can be reliably obtained, the hardness of the surfaces of the rotors 11 and 13 can be increased, and the durability and the sliding portion can be improved. The wear resistance can be reliably improved.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the internal gear pump, the rotor manufactured by the manufacturing method of the present invention may be both the outer rotor and the inner rotor, or only one of them.

[0015]

According to the method for manufacturing a rotor for an internal gear pump of the present invention, after a work is subjected to a grinding process, the work is subjected to a steam treatment to form an oxide film on the surface of the work. The entire rotor thus obtained is reliably covered with the oxide film, the effect of the oxide film can be reliably obtained, and the durability performance and the wear resistance of the sliding portion can be reliably improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a method for manufacturing a rotor for an internal gear pump according to the present invention, wherein (a) shows a state after a grinding step and (b) shows a state after a coating step.

FIG. 2 is a front view of the internal gear pump.

FIG. 3 is a sectional view of an internal gear pump.

FIG. 4 is a cross-sectional view showing an example of a method for manufacturing a conventional rotor for an internal gear pump.
(B) shows the state after the grinding step.

[Explanation of symbols]

 1 Housing 11 Outer rotor (work) 13 Inner rotor (work) 17 Oxide coating

Claims (2)

[Claims] 1. A method of manufacturing a rotor for an internal gear pump made of a sintered material slidably housed in a housing made of a high silicon-containing material, wherein the raw material powder is compressed to form a green compact. A forming step, a sintering step of heating and sintering the green compact, a grinding step of performing a grinding process on a work made of a sintered body obtained in the sintering step, and steaming the work after the grinding step. A process for forming an oxide film on the surface of the work by performing a process. 2. A method of manufacturing a rotor for an internal gear pump made of an iron-based sintered material slidably housed in a housing made of a high silicon aluminum-containing material. A powder molding step of molding, a sintering step of heating and sintering the green compact, a straightening step of pressing and molding a work made of a sintered body obtained in the sintering step, and a straightening step of the straightening step. A cutting process of performing a cutting process on the work later, a grinding process of performing a grinding process on the work after the cutting process, and a coating process process of performing a steam treatment on the work after the grinding process to form an oxide film on the surface of the work. A method for manufacturing a rotor for an internal gear pump, comprising: